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Nutrient loading diminishes the dissolved organic carbon drawdown capacity of seagrass ecosystems

journal contribution
posted on 2020-10-01, 00:00 authored by S Liu, Y Deng, Z Jiang, Y Wu, X Huang, Peter Macreadie
Seawater dissolved organic carbon (DOC) in seagrass meadows is gaining attention for its role in carbon sequestration. Abundant refractory compounds in DOC are exported by seagrass meadows to the deep sea, thereby contributing to long-term carbon drawdown. DOC lability and bacterioplankton communities are key determining factors in this carbon sequestration process, and it has been hypothesized that these may be affected by nutrient loading – however, scientific evidence is so far weak. Here, we studied the response of DOC composition and bacterioplankton communities to nutrient loading in seagrass meadows of the South China Sea. We found that increasing nutrient loads enhanced nitrogen and phosphorus concentrations in DOC, which promoted algae blooms (i.e. epiphyte, phytoplankton and macroalgae) in seagrass meadows, and presumably increased the lability of DOC and its bioavailability to microbes. Also, the relative abundance of K-strategist bacterioplankton communities with the potential to degrade refractory compounds (Acidimicrobiia, Verrucomicrobiales and Micrococcales) increased in the seagrass meadows exposed to high nutrient loads. These results suggest that high nutrient loading can enhance labile DOC composition, and thus increase refractory DOC remineralization rate, thereby weakening the DOC contribution potential of seagrass meadows to long-term carbon sequestration.

History

Journal

Science of the total environment

Volume

740

Article number

140185

Pagination

1-8

Location

Amsterdam, The Netherlands

ISSN

0048-9697

eISSN

1879-1026

Language

eng

Publication classification

C Journal article, C1 Refereed article in a scholarly journal

Publisher

Elsevier